If I buy the iPad 2 without 3G, can I purchase/add 3G later on somehow? Or do you have to initially buy the 3G with the iPad in order to use it at all?
iPads have 2 versions in the second gen. That's the 3G/wifi compatible and a wifi only one. If you buy the wifi only. No, there is no way to do so. It doesn't have the internal parts needed to get 3G service. If you purchase the 3G/wifi than yes. You don't need to purchase 3G every month. its a pay as you go type of thing.